Does the temperature of a steam supply pipe have to be over 212 Degrees?

Todd_33

I've got a 9 unit apartment building and one of the radiators at the end of the steam run heats very slowly. There is a 3 foot branch pipe that comes off the main. I measured the temp of the main where the branch joined and it was 190 degrees. there was little steam going into the branch as 18" away from main it was around 80 degrees. I've previously installed ample venting on the radiator ( I think ) I'm thinking the main is losing heat and the steam is condensing a little before it gets to the branch. 1929 boiler system, piping intact I think. The branch was lengthened when we moved the radiator back a little. I'm in Milwaukee, Wisconsin. Is this a possibility? I measured the temp with a recently purchased infrared gun with laser. Thank you..Todd

Mad Dog_2

How are your main vents on that run?  Boiler HP can be running 🏃‍♂️ shy too..running 🏃‍♂️ out of steam...More details.  Mad Dog 🐕 

Todd_33

main venting should be ok - 3 or 4 groton #2, BP maybe 3-4 lbs. Not sure what "out of steam" , "shy too" means. I appreciate the reply =

mattmia2

usually steam stopping somewhere in a main with adequate venting means there is liquid water in the main that is cooling and condensing the steam in to water

EBEBRATT-Ed

Water boils at 212 degrees. That varies a little bit by the altitude above sea level, so 212 is the # usually used.

I agree with @mattmia2 that water in a low spot will stop the steam. Check pipes and radiator's for proper pitch.

You could remove a radiator vent and install a 1/8" petcock or valve and leave it wide open just for a test to see if you get steam at the radiator then shut it and re install the vent.

Todd_33

So, the main should be 212+ degrees? On a 1 pipe system, I wonder if the returning condensate is cooling the steam? as i say, this is the last radiator on this main.. I do have a similar problem with the last rad on a different main as well... This has been happening since I bought the building, maybe 17 years ago...

Jamie Hall

Couple of things. One is that you are measuring the temperature of the main. Which worries me badly. Are these mains insulated? If there is one inch insulation -- even half inch -- they won't be that hot on the outside of the insulation, that's what it's there for after all -- but it is the main metal temperature you want.

And... if they aren't insulated, you may simply be losing too much heat in the main and building condensate which, as has been said, will stop your steam dead.

The insulation isn't there to keep the main hot. It's there to keep the steam from condensing too much, too soon.

Second, check the pitch of the pipes very carefully. One pipe steam particularly needs ample, continuous pitch or, again, you will get pooled condensate which will stop the steam dead.

Lat -- for now -- you mention "BP [I assume boiler pressure] 3 to 4 pounds". Not good. The absolute top pressure should be 2 pounds cutout, and 1 and a half would be better. Easy to fix, so do it. While that probably isn't the cause of the problem, it surely isn't helping.

Todd_33

Jamie Hall.. thanks for the comments.. the mains are insulated, maybe 1 inch thick fiberglass. There is about a 6" section where insulation is missing where I take the temp. Re system pressure.. I'm using a Honeywell vapostat (?) And I recall having a problem getting the pressure that low.. it's been awhile so I'll revisit that, thanks for the tip. I had a leaking flange / joint replaced in the header a few years ago and never re-insulated  that 48" section of 5" (?) pipe. It's been on the Todo list.. I'll do that too.   So.. that main should be 212° or more? Maybe a dumb question but ...  Thanks 

Jamie Hall

Well, it should be close, but it will be a little less. Certainly over 200, though. But. It can be difficult to get an accurate reading with an IR non-contact thermometer. They have been known to read low -- sometimes very low. Better, if your multimeter came with a thermocouple and a temperature range (some do, some don't) is to strap the thermocouple tightly to the pipe -- even string will do -- and see what that reads.

bburd

You might consider slowing the venting on the other radiators to get more steam to the slow one.

ChrisJ

How are you measuring the temperature of the pipe?
Have you used the same method on others and if so, what temperature did you see?

BobC

Ir thermometers are sensitive to the color of what is being measured and it's reflectivity. Yry puttinyb a piece of painters tape on what your trying to measure.

Bob

ethicalpaul

Cold/warm condensate will stop steam for sure, but I don't think it's true that all condensate will. For reference: any counterflow system.

If your boiler is anywhere near appropriately sized to your radiation (and it almost certain that it is oversized), it is impossible for it to run out of steam for some radiators. Likewise, uninsulated main pipes won't cause this either...again, because there is a ridiculously high ~30% capacity built into the rating to handle this.

However, a very similar-looking situation can result if you have too much venting at various radiators. At the start of a call for heat, they will take all the steam they can until their vents close (or they become fully hot) which can leave other radiators/parts of your main not seeing steam until that time (and that can be a long time because a cool radiator can suck up a LOT of steam before its vent closes and/or it gets fully hot.

@bburd 's concise post above that I agree with is pointing to this issue: https://forum.heatinghelp.com/discussion/comment/1765457/#Comment_1765457

The key is to start with all of your radiators venting very slowly (like a Gorton #4 capacity) then very minimally and carefully increase the venting in those rooms that are cold.

ChrisJ

BobC said:

Ir thermometers are sensitive to the color of what is being measured and it's reflectivity. Yry puttinyb a piece of painters tape on what your trying to measure.

Bob

There's also distance.
You can't be 10 feet from a 2" pipe with an IR thermometer. You'd need to be an inch from it.

Todd_33

Ethicalpaul, I see what you are saying.. I'm wondering how to do that with 9 units with 5 radiators each. Communication with tenants is spotty and inaccurate if asking about timing and intensity of radiator heating.. any thoughts on that? Also changing all those vents.. uugh.. time and $$$. Thanks for the ideas .. 

ethicalpaul

You have my sympathy, it's not easy. I do think good tenant communication helps, but there are some things that can assist you.

Honestly I missed that this was a 9 unit building, I apologize for that, you won't be able to just put #4 vents on every radiator. It is going to depend on a lot of variables...do the risers have vents, for example.

If it were me, I want to start with at least a map of what vents were on each radiator, what risers had vents, and a conversation with each tenant about what rooms are too hot and what ones are too cold.

I think having non-adjustable vents would help reduce some of the uncertainty. Gorton is good but they are $$$. Maid O Mist is good but the tenants might remove the orifice, causing havoc.

If you can attach a remote temperature sensor to a central large radiator in each unit, that can give you some useful timing information, but it depends on how deep you want to get into this.

Here in NYC the buildings all just seem to crank the pressuretrol up to 5-10 psi and let 'em whistle and let the tenants just open their windows as needed. It's not pretty.